Re: [Qemu-devel] [PATCH v4 3/5] acpi: pc: add fw_cfg device node to ssdt

[Laszlo Ersek <lersek@redhat.com>]

On 10/01/15 13:33, Igor Mammedov wrote:
> On Thu, 1 Oct 2015 10:27:15 +0200
> Laszlo Ersek <lersek@redhat.com> wrote:
> 
>> On 10/01/15 09:02, Igor Mammedov wrote:
>>> On Sun, 27 Sep 2015 17:29:00 -0400
>>> "Gabriel L. Somlo" <somlo@cmu.edu> wrote:
>>>
>>>> Add a fw_cfg device node to the ACPI SSDT, on machine types
>>>> pc-*-2.5 and up. While the guest-side BIOS can't utilize
>>>> this information (since it has to access the hard-coded
>>>> fw_cfg device to extract ACPI tables to begin with), having
>>>> fw_cfg listed in ACPI will help the guest kernel keep a more
>>>> accurate inventory of in-use IO port regions.
>>>>
>>>> Signed-off-by: Gabriel Somlo <somlo@cmu.edu>
>>>> ---
>>>>  hw/i386/acpi-build.c | 23 +++++++++++++++++++++++
>>>>  hw/i386/pc_piix.c    |  1 +
>>>>  hw/i386/pc_q35.c     |  1 +
>>>>  include/hw/i386/pc.h |  1 +
>>>>  4 files changed, 26 insertions(+)
>>>>
>>>> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
>>>> index 95e0c65..ece2710 100644
>>>> --- a/hw/i386/acpi-build.c
>>>> +++ b/hw/i386/acpi-build.c
>>>> @@ -906,6 +906,7 @@ build_ssdt(GArray *table_data, GArray *linker,
>>>>             PcPciInfo *pci, PcGuestInfo *guest_info)
>>>>  {
>>>>      MachineState *machine = MACHINE(qdev_get_machine());
>>>> +    PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(machine);
>>>>      uint32_t nr_mem = machine->ram_slots;
>>>>      unsigned acpi_cpus = guest_info->apic_id_limit;
>>>>      Aml *ssdt, *sb_scope, *scope, *pkg, *dev, *method, *crs, *field, *ifctx;
>>>> @@ -1071,6 +1072,28 @@ build_ssdt(GArray *table_data, GArray *linker,
>>>>      aml_append(scope, aml_name_decl("_S5", pkg));
>>>>      aml_append(ssdt, scope);
>>>>  
>>>> +    if (!pcmc->acpi_no_fw_cfg_node) {
>>> we don't really care about SSDT size changes since during
>>> migration ACPI blobs will be migrated from source, so
>>> machine compat bloat is excessive here. It would be better
>>> to just remove it.
>>
>> This was Eduardo's suggestion, if I recall correctly:
>>
>> http://thread.gmane.org/gmane.comp.emulators.qemu/361930/focus=361983
>>
>> The idea being, if you move a guest from older QEMU to newer QEMU, but
>> keep the machine type (or more precisely, the full machine config, like
>> the domain XML) intact, the ACPI device node should not appear out of
>> the blue.
> This ACPI device is an always used resource declaration regardless
> of machine type so it makes sense to tell guest about used resource.
> 
> The only reason for machine compat code would be if guest suddenly
> started to ask for a driver but as Gabriel showed with _STA(0xB)
> it doesn't, so I'm trying to keep ACPI code machine compat agnostic
> as much as possible.

Fine by me, but I think Eduardo should agree (or disagree) as well,
because it was his point originally.

> 
> 
> PS:
> is it me alone or email to qemu-devel arrives with huge delay (upto 2 days)?

Several subscribers have reported the same, and I'm seeing delays myself.

Thanks
Laszlo

> 
>>
>> I'll let Gabriel answer your other question below. :)
>>
>> Thanks
>> Laszlo
>>
>>
>>>
>>>
>>>> +        scope = aml_scope("\\_SB");
>>>> +        dev = aml_device("FWCF");
>>>> +
>>>> +        aml_append(dev, aml_name_decl("_HID", aml_string("QEMU0002")));
>>>> +        /* device present, functioning, decoding, not shown in UI */
>>>> +        aml_append(dev, aml_name_decl("_STA", aml_int(0xB)));
>>>> +
>>>> +        crs = aml_resource_template();
>>>> +        /* when using port i/o, the 8-bit data register *always* overlaps
>>>> +         * with half of the 16-bit control register. Hence, the total size
>>>> +         * of the i/o region used is FW_CFG_CTL_SIZE */
>>>> +        aml_append(crs,
>>>> +            aml_io(AML_DECODE16, FW_CFG_IO_BASE, FW_CFG_IO_BASE,
>>>> +                   0x01, FW_CFG_CTL_SIZE)
>>>> +        );
>>> could you check/dump this _CRS and PCI0._CRS to see if they are intersecting
>>> in any way?
>>>
>>>
>>>> +        aml_append(dev, aml_name_decl("_CRS", crs));
>>>> +
>>>> +        aml_append(scope, dev);
>>>> +        aml_append(ssdt, scope);
>>>> +    }
>>>> +
>>>>      if (misc->applesmc_io_base) {
>>>>          scope = aml_scope("\\_SB.PCI0.ISA");
>>>>          dev = aml_device("SMC");
>>>> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
>>>> index 3ffb05f..7f5e5d9 100644
>>>> --- a/hw/i386/pc_piix.c
>>>> +++ b/hw/i386/pc_piix.c
>>>> @@ -482,6 +482,7 @@ static void pc_i440fx_2_4_machine_options(MachineClass *m)
>>>>      m->alias = NULL;
>>>>      m->is_default = 0;
>>>>      pcmc->broken_reserved_end = true;
>>>> +    pcmc->acpi_no_fw_cfg_node = true;
>>>>      SET_MACHINE_COMPAT(m, PC_COMPAT_2_4);
>>>>  }
>>>>  
>>>> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
>>>> index 1b7d3b6..7180ca3 100644
>>>> --- a/hw/i386/pc_q35.c
>>>> +++ b/hw/i386/pc_q35.c
>>>> @@ -385,6 +385,7 @@ static void pc_q35_2_4_machine_options(MachineClass *m)
>>>>      pc_q35_2_5_machine_options(m);
>>>>      m->alias = NULL;
>>>>      pcmc->broken_reserved_end = true;
>>>> +    pcmc->acpi_no_fw_cfg_node = true;
>>>>      SET_MACHINE_COMPAT(m, PC_COMPAT_2_4);
>>>>  }
>>>>  
>>>> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
>>>> index 86007e3..6d0f1bd 100644
>>>> --- a/include/hw/i386/pc.h
>>>> +++ b/include/hw/i386/pc.h
>>>> @@ -62,6 +62,7 @@ struct PCMachineClass {
>>>>      bool broken_reserved_end;
>>>>      HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
>>>>                                             DeviceState *dev);
>>>> +    bool acpi_no_fw_cfg_node;
>>>>  };
>>>>  
>>>>  #define TYPE_PC_MACHINE "generic-pc-machine"
>>>
>>
>